Devastating AssaultSource Weapon Master's Handbook pg. 22
You can hammer at a foe to smash through its defenses.
Prerequisites: Base attack bonus +9, weapon training class feature with a melee weapon.
Benefit: As a full-round action, you can bat aside all of your foe’s defenses to ensure you make a single, especially effective melee attack. You make a single melee attack using an appropriate weapon against a single target, but make as many attack rolls as you could in a full-attack action using that weapon. You make the attack rolls in order from highest bonus to lowest, as if you were making a full attack. If any of the attack rolls hit the target, your single attack is considered to have hit and you roll damage normally. If one or more rolls are critical threats, you confirm the critical hit only once using your highest base attack bonus.
If you hit with two or more attacks, the target must succeed at a Fortitude save (DC = 10 + 1/2 your base attack bonus + your Strength modifier) or suffer a condition for 1d4 rounds. If at least two attacks hit, you can choose from deafened, entangled, or shaken. If at least three attacks hit, you can also choose from blinded or staggered. If at least four attacks hit, you can also choose the dazed condition. Once you have forced a foe to attempt a saving throw to avoid suffering a condition via this feat, you cannot attempt to inflict that condition on it again with Devastating Assault for 24 hours.